I awake Sunday morning, bleary-eyed and not entirely sure how I can possibly face the day of physical exertion ahead.

I have agreed to go canyoning at Piha, a short 40 minute drive from downtown Auckland. ‘Canyoning': the sense of adventure evoked by the word has convinced me to join my friends’ escapade, without really knowing what I am in for.

We arrive in Piha and, being helplessly urbane Aucklanders, immediately seek out coffee. Coincidentally, the Piha cafe is also the spot where we meet our guides from AWOL Canyoning Adventures. Javier and Conor enter on cue, two men with a wealth of experience. Javier hails from Chile and was previously a mountaineer. He has worked as a horse trek guide in the Andes and most recently as a glacier guide in New Zealand’s South Island. Conor is a West Auckland local, who works at AWOL over the summer then travels to Italy for various outdoor guiding pursuits during our winter. It’s fair to say we feel we are in safe hands.

We take a short drive to the site and run through a safety briefing, before beginning the day’s real journey with a hike through a classic New Zealand forest scene of ferns and nikau palms. Despite the slope of the track, the casual pace affords me a great chance to meet everyone around me. Today’s group comprises a few locals, a group of Germans and an Irish couple. As one of those locals, I am very familiar with the Waitakere bush, so it is a joy to vicariously experience this landscape through the eyes of these guests from further afield. The hike feels brief, and soon enough we emerge onto a rocky plateau, where our descent is to begin.

To set the scene for what’s to come, our first challenge is to jump into a rock pool full of very fresh water. I’m shocked awake and feel utterly invigorated. It also feels cleansing; the sweat of our ascent is washed away, and any vanities we were clinging on to are collectively gone. Fortunately, the wetsuits we have been provided are thick and it doesn’t take long to develop an insulating layer of warmed water.

We undertake our first abseil alongside the waterfall fed by this pool. Conor goes first, enabling him to spot us from the bottom. He glides down in a confident and seamless motion. Then it’s our turn. I step up, awkwardly shuffling to the edge and easing into the ropes, wary of their tensile strength. It doesn’t take long to realise how irrational my fears are and before long, I’ve committed to the experience completely. The descent is quick and – flush with adrenaline – I start yearning for another, bigger rush, a wish I soon see granted.

Our next abseil offers a thrilling twist: descending a cliff face inside a waterfall. The water has cut a narrow channel through the rock and it creates a deafening roar. There’s no denying the rush of the experience – as I descend, I allow myself the fleeting escapism of pretending to be an adventurer delving into the unknown. At the bottom, we uncouple from our harnesses in churning, waist-deep waters.

An enormous stump blocks our way, firmly wedged between the cliff faces. I learn that it is a remnant from kauri logging days. Foresters would fell these native trees for their incredibly versatile, straight trunks, then send them downstream for milling. The culling of these giants strikes me as immensely depressing. However, we clamber over the trunk and suddenly the environment feels very different. The canyon widens, the water calms and birdsong can be heard again. The towering walls and the inaccessible nature of this area makes it feel like a hidden oasis.

We wade onto shore and I’m immediately awestruck when I catch sight of a huge shadow slinking through the water. The silt makes it difficult to see but there’s no denying its size. Javier and Conor explain it’s an eel they frequently spot in these waters. I consider that I have only just walked through the area this disconcerting creature now occupies and feel uneasy: what other secrets do these rivers hold?

Our group tracks the river downstream. Along the way are mini-challenges to keep us on our toes: squeezing under rocks and through tight spaces. For those who get queasy in such situations, our guides offer alternatives – but they are wonderfully encouraging, and members of our group are frequently persuaded to overcome their fears.

The journey culminates with another waterfall, which appropriately also happens to be the biggest. Fortunately, by this stage we are all seasoned professionals and the descent is a breeze. We land at a popular swimming hole, the perfect spot for lunch. We kick back in the blazing summer sun among sunbathers and picnickers and reflect on our accomplishments.

This journey offers more than abseiling: I leave the canyon feeling revitalised. As I throw back an icy beer in the afternoon sun to cap off our adventure, I consider how I would otherwise have spent my Sunday, and feel grateful that I challenged myself.